Air conditioning system

ABSTRACT

An air conditioning system for office buildings is provided wherein relatively warm secondary air heated by light fixtures, etc. in the ceiling plenum above the false ceiling is added to relatively cool preconditioned primary air from a heat exchanger in an air induction box and exhausted from the induction box and moved to the office space below the false ceiling. A constant capacity air exhaust blower in the air induction box functions to exhaust a constant volume of the mixture of primary air and secondary air from the ceiling plenum to the office space. The rate of flow of the relatively cool primary air to the induction box is varied in response to the temperature of the office space, and the rate at which the relatively warm secondary air is induced to flow from the ceiling plenum into the air induction box is inversely proportional to the rate of flow of primary air moving into the air induction box.

llnite States Patent augherty, Jr.

[ 51 Dec. 30, 1975 [76] Inventor:

[22] Filed:

AIR CONDITIONING SYSTEM Carl Francis Daugherty, Jr., PO.

Box 28617, Atlanta, Ga. 30328 Mar. 25, 1974 Appl. No.: 454,596

Primary Examiner-William E. Wayner Attorney, Agent, or Firm-Jones, Thomas & Askew [57] ABSTRACT An air conditioning system for office buildings is provided wherein relatively warm secondary air heated by light fixtures, etc. in the ceiling plenum above the false ceiling is added to relatively cool preconditioned primary air from a heat exchanger in an air induction box and exhausted from the induction box and moved to the office space below the false ceiling. A constant capacity air exhaust blower in the air induction box functions to exhaust a constant volume of the mixture of primary air and secondary air from the ceiling plenum to the office space. The rate of flow of the relatively cool primary air to the induction box is varied in response to the temperature of the office space, and the rate at which the relatively warm secondary air is induced to flow from the ceiling plenum into the air induction box is inversely proportional to the rate of flow of primary air moving into the air induction box.

7 Claims, 2 Drawing Figures US. Patant D60. 30, 1975 MMMMM/mv/MAisw/mm AIR CONDITIONING SYSTEM BACKGROUND OF THE INVENTION A typical office building is constructed with a dropped false ceiling fabricated from a suspended latticework of support bars and acoustical tiles laid in the support bars. Lighting fixtures, heat ducts, electrical wiring, plumbing conduits, and various other devices are present in the ceiling plenum, and the air in the ceiling plenum is usually relatively warm because of the heat emitted from lighting fixtures and other relatively hot elements in the ceiling plenum and because of the air at or slightly above room temperature returning to the central air conditioner recirculating fan passing from the room through the ceiling plenum.

Various air conditioning systems have been developed which use the relatively warm air in the ceiling plenum to heat the primary ventilating air moved into the office space. In a typical prior art air conditioning system, a source of relatively cool primary air is moved from a heat exchanger through a network of conduits to a mixing box in the ceiling plenum, and the relatively warm air in the ceiling plenum is mixed with the primary air and the mixed air is moved downwardly through the suspended ceiling into the office space below. The typical mixing box is an air induction box which directs the relatively cool primary air through a venturi, and the flow of air through the venturi causes the relatively warm air from the ceiling plenum to be drawn into the induction box and mixed with the relatively cool primary air.

The mixture of relatively cool primary air and relatively warm secondary air is controlled by a thermostat in the room to which the mixture of air is being delivered, and the thermostat usually controls either the rate of flow of primary air into the induction box, or the opening in the induction box for the secondary air, or both. The typical system causes a varying rate of flow of mixed air into the office space, which is occasionally disconcerting to the personnel working in the office space, and the supply of mixed air to the office space is occasionally too little or too much to provide proper ventilation. Moreover, in a system which reduces the rate of flow of primary air into the induction box in response to a drop in temperature in the office space, the flow of air into the office space is virtually cut off under some circumstances, and no heated air is moved into the office space.

SUMMARY OF THE INVENTION Briefly described, the present invention comprises an air conditioning system for an office building having a dropped ceiling which defines a ceiling plenum in which the air is heated by light fixtures and air returning from office space and the relatively warm air in the ceiling plenum is mixed with relatively cool preconditioned primary air, and the mixture of air is moved to the office space below the dropped ceiling. Powered air induction mixing boxes are located in the ceiling plenum, and a constant volume blower in each mixing box exhausts air from the mixing boxes and forces the air at a constant rate into the office space. Each mixing box defines unrestricted openings through which the relatively warm ceiling plenum air can enter, and the relatively cool preconditioned primary air is directed to the mixing box. The flow of relatively cool preconditioned primary air is regulated by a valve which responds to the room temperature, and the relatively warm secondary air from the ceiling plenum is induced to flow into the mixing box in inverse relationship to the flow of primary air into the mixing box to supply sufficient air to the exhaust blower in the mixing box. The blower therefore draws air at a constant rate from the mixing box as supplied by the primary air stream and as induced from the ceiling plenum.

Thus, it is an object of the present invention to provide an air conditioning system which uses a source of preconditioned cool primary air and ceiling plenum air as a source of warm air and mixes the primary air with the ceiling plenum air at varying rates in response to the temperature in the office space and supplies the mixed air at a constant rate to the office space.

Other objects, features and advantages of the present invention will become apparent upon reading the following specification, when taken in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 illustrates a portion of an air conditioning system, and shows a powered air induction box positioned in a ceiling plenum and a primary air conduit.

FIG. 2 is a schematic cross sectional illustration of the powered air induction box.

DESCRIPTION OF AN EMBODIMENT Referring now in more detail to the drawing, in which like numerals indicate like parts throughout both views, FIG. 1 illustrates a portion 10 of an air conditioning system located in the ceiling plenum 11 of an office building or the like. The ceiling plenum l 1 is formed by the overhead superstructure 12 for the floor next above or the roof and a dropped false ceiling l3 suspended below the ceiling superstructure. The false ceiling can be of any conventional type, such as the conventional latticework of support bars and rectangles of acoustical tile suspended in the latticework. Various lighting fixtures 14 are located in the false ceiling and arranged to emit light to the office space below the false ceiling. The heat from the light fixtures and possibly from other sources in the ceiling plenum accumulates in the return air space in the ceiling plenum. Ceiling return grill 47 allows the room air to be returned to the ceiling plenum, and hence to the central air conditioner fan.

The air conditioning system includes a heat exchanger and a blower system (not shown) to supply preconditioned primary air to the office space below the false ceiling, and the ductwork 1S communicates with the heat exchanger and blower and extends through the ceiling plenum 11. Branch conduits such as branch conduit 16 are connected between the main conduit 15 which carries the preconditioned primary air and the mixing boxes 18 which are located throughout the ceiling plenum. A delivery conduit 17 extends from the other end of each mixing box 18 and delivers air in a downward direction through a vent opening 20 formed in the acoustical tile of the false ceiling 13.

As is illustrated in FIG. 2, the air induction mixing box 18 comprises a rectangular housing 19 having side walls 20 and opposed end walls 21 and 22. A primary air conduit 24 enters housing 19 through its first end wall 21 and extends beyond the end wall a substantial distance into the housing 19. The primary air conduit 24 functions as aprimary air inlet for the housing so as to supply the preconditioned, relatively cool primary air to the mixing box. Secondary air inlet openings 25 are formed in the housing 19 adjacent the entrance of the primary air conduit 24 into the housing, and function as secondary air inlets for allowing the relatively warm ceiling plenum air to enter housing 19. Centrifugal blower 26 is mounted in housing 19, and its exhaust duct 27 extends through the second end wall 22. Centrifugal blower 26 functions as fan means to move or exhaust air from the housing, and the exhaust duct 27 functions as an air outlet for the housing.

Primary air conduit 24 includes a venturi restriction 30 upstream from the outlet opening 31 of the conduit. A valve support rod 32 extends longitudinally through primary air conduit 24 and its venturi restriction 30, and ball valve 34 is mounted on and is movable with valve support rod 32. Collar 35 is rigidly mounted on valve support rod 32 inside ball valve 34 and coil compression spring 36 is wound about valve support rod 32 and extends between collar 35 and the upstream side of ball valve 34. The arrangement of the spring, collar and ball valve on valve support rod 32 is such that the ball valve 34 is movable against the bias of coil compression spring 36 along the length of valve support rod 32, toward and away from venturi restriction 30.

Valve support rod 32 is movable along the length of primary air conduit 24 by means of linkage 38 and 39 and pneumatic control ram 40. Pneumatic control ram 40 is pneumatically connected to a thermostat 41 by means of flow line 42, and thermostat 41 is placed in the office space to which the air from mixing box 18 is delivered.

Sound baffle 44 is suspended in housing 19 in alignment with outlet opening 31 of primary air conduit 24. Sound baffle 44 is shaped like a truncated pyramid with its convex surface extending toward outlet opening 31 of primary air conduit 24 and is fabricated from a foraminous material so as to attenuate noise emitted from the outlet opening 31 of primary air conduit 24. The inside surfaces of side walls 20 and end walls 22 are coated with a sound dampening material 43.

Centrifugal blower 26 is continuously driven by constant speed motor 45 and functions to exhaust air at a constant rate through exhaust duct 27. lf desired, a heat exchanger 46 is mounted in the exhaust duct 27. The heat exchanger can be of any conventional electrical or fluid design, and can be thermostatically controlled, if desired, and when it is operated the heat exchanger 46 functions to heat the air exhausted through exhaust duct 27.

In the operation of the air conditioning system, the primary air is delivered from the main primary air conduit through branch conduit 16 into primary air conduit 24 of the mixing box 18. The centrifugal blower 26 functions as a fan means for exhausting air from within the mixing box 18, and the exhaust duct 27 from the blower 26 functions as an air outlet, and the air is delivered from the outlet through the delivery conduit 17 and then downward through the opening in the false ceiling or through other air passages to the office below.

Centrifugal blower 26 operates at a substantially constant speed and therefore exhausts air from mixing box 18 at a substantially constant rate. The speed of motor 45 and the capacity of centrifugal blower 26 are chosen so that the constant exhaustion of air from mixing box 18 will be approximately equal to the normal full capacity delivery of primary air through primary air conduit 24 into mixing box 18. Thus, when the valve means in primary air conduit 24 is in its full open position, the volume of primary air delivered to mixing box 18 per unit of time will be equal to the volume of air exhausted from the mixing box by centrifugal blower 26 per unit of time, and no secondary air will be induced to flow from ceiling plenum 11 through the secondary air openings 25 and into the mixing box.

The ball valve 34 and venturi restriction 30 function as valve means for regulating the flow of primary air through the primary air inlet. When the temperature increases in the office to which the air is delivered, the thermostat 41 in the office will cause a change in the air pressure supplied to the control ram 40, which causes a distention of the linkage 39 and a corresponding counterclockwise pivotal movement of linkage 38, to move valve support rod 32 and its ball valve 34 to the left, or upstream with respect to the flow of primary air into mixing box 18, thus creating a larger opening at venturi restriction 30 and allowing a larger volume of primary air to move into mixing box 18.

Since centrifugal blower 26 functions to exhaust air at a substantially constant rate from mixing box 18, less air will be induced to flow from ceiling plenum 11 through secondary air openings 25 and into the mixing box when the supply of primary air to the mixing box is increased.

When the temperature decreases in the office space to which the air is delivered from mixing box 18, thermostat 41 will function to move control ram in the opposite direction, causing ball valve 34 to move to the right, or downstream and toward venturi restriction 30, thus restricting the air flow through the valve means and slowing the rate of delivery of primary air to the mixing box 18. Centrifugal blower 26 then functions to induce a larger amount of relatively warm secondary air to move from ceiling plenum 11 through secondary air inlet 25 and into the mixing box to mix with the primary air.

The centrifugal blower 26 runs at a constant speed so as to exhaust air from mixing box 18 at a constant rate, so as to provide a constant external static pressure in the office space to which the air is delivered. The system allows substantially full regain of heat released into the ceiling plenum before any reheat is acquired by heat exchanger 46. The movable arrangement of ball valve 34 on its valve support rod 32 allows primary air to be delivered through primary air conduit 24 at a substantially constant rate in spite of rapid changes in the pressure of the air moving through the primary air conduits, since as the pressure upstream of the ball valve 34 increases and the flow through the valve means is inclined to increase, the spring 36 contracts to provide more restriction through the valve means, so that the air delivered through the opening 31 of the primary air conduit 24 is at a constant rate of delivery. Should the pressure in the primary air conduit 24 become reduced, the coil compression spring 36 would function to move ball valve 34 along its valve support rod 32 further away from venturi restriction 30, thus opening the restriction of the valve and thus continuing to maintain a substantially constant rate of flow of primary air which is independent of pressure changes upstream or downstream of the valve means.

While this invention has been described in detail with particular reference to a preferred embodiment thereof, it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinbefore and as defined in the appended claims.

I claim: i

1. An air induction box comprising a, housing with side walls and opposed end walls, a primary air conduit entering said housing through a first end wall and extending into said housing with its end opening extending toward the second end wall, at least one unrestricted secondary air inlet opening in said housing adjacent the entrance of said primary air conduit into said housing, a substantially constant speed centrifugal blower in said housing including an exhaust conduit extending through the second end wall arranged to continuously exhaust mixed air from said housing at a substantially constant rate, a sound baffle in said housing, valve means in the portion of said primary air conduit extending into said housing for selectively decreasing or increasing the flow of primary air through said primary air conduit, said valve means comprising a venturi in said primary air conduit, a valve support rod in said primary air conduit upstream from said venturi movable along its length toward and away from said venturi, a valve ball mounted on and movable with said valve support rod toward and away from said venturi and spring means connected between said valve ball and said valve support rod and arranged to permit relative movement between said valve ball and said valve support rod and to bias said valve ball away from said venturi, whereby the valve ball moves along the length of the valve support rod in response to differential air pressure across the valve ball and regulates the flow of primary air into the housing.

2. Air air induction box comprising a housing, a primary air conduit entering said housing, at least one unrestricted secondary air inlet opening in said housing, a substantially constant speed blower arranged to continuously exhaust mixed air from said housing at a substantially constant rate, valve means in said primary air conduit for selectively decreasing or increasing the flow of primary air through said primary air conduit, said valve means comprising a venturi in said primary air conduit, a valve support rod in said primary air conduit upstream from said venturi movable along its length toward and away from said venturi, a valve ball mounted on and movable with said valve support rod toward and away from said venturi and spring means connected between said valve ball and said valve support rod and arranged to permit relative movement between said valve ball and said valve support rod and to bias said valve ball away from said venturi, whereby the valve ball moves along the length of the valve support rod in response to differential air pressure across the valve ball and regulates the flow of primary air into the housing.

3. An air induction box for use in a ceiling plenum with an air conditioning system that provides a flowof primary air, said induction box comprising a housing with a primary air inlet conduit for connection to the flow of primary air of the air conditioning system, a constantly open secondary air inlet for continuous constant pressure open communication with the ceiling plenum, an air outlet, an air outlet fan means arranged to move air from said housing through said air outlet, and valve means positioned in said primary air inlet conduit for regulating the flow of primary air through said primary air inlet conduit, said valve means comprising a venturi, a valve member positioned upstream of said venturi and movable toward and away from said venturi to reduce and increase the flow of primary air through said primary air inlet conduit and into said 6 induction box and spring means biasing said valve member 'away from said venturi to permit the valve member to move toward and away from said venturi in response to changes in pressure upstream of said venturi, whereby when the valve means reduces the flow of primary air into the housing the fan means induces more air to flow from the ceiling plenum through the secondary air inlet and into the housing, and when the valve means increases the flow-of primary air into the housing the fan means induces less air to flow from the ceiling 'plenum through the secondary air inlet and into the housing, and the spring means moves the valve member away from the venturi in response to a decrease in pressure in the primary air moving into the induction box and allows the valve member to move toward the venturi in response to an increase in pressure in the primary air moving into the induction box to maintain a substantially constant flow of primary air into the induction box in spite: of rapid changes in pressure of the primary air moving into the induction box.

4. The air induction box of claim 3 and wherein said primary air inlet conduit comprises a conduit extending through a first end of said housing with an outlet opening spaced away from said one end of said housing, and wherein said valve means is positioned in a portion of said primary air inlet conduit which is located within said housing.

5. An air ventilating process for a room having a ceiling plenum and an air induction box located in the ceiling plenum with a constantly open secondary air opening defined in the induction box comprising the steps of moving primary air at a first temperature through a conduit into the air induction box to a position downstream of the secondary air opening, continuously exhausting air from the air induction box at a substantially constant rate from a position downstream from the position where the primary air is moved from its conduit into the induction box and directing the exhausted air to the room below the ceiling, reducing the flow of primary air to the: air induction box in re sponse to a change in an external condition while continuing to exhaust air from the air induction box at a substantially constant rate so as to induce more air to flow from the ceiling plenum through the secondary air opening and into the air induction box, and increasing the flow of primary air to the air induction box in response to a change in an external condition while continuing to exhaust air from the air induction box at a substantially constant rate so as to induce less air to flow from the ceiling plenum through the secondary air opening and into the air induction box, and maintaining a substantially constant flow of primary air to the air induction box in spite of rapid increases or decreases in pressure of the primary air moving toward the air induction box.

6. The system of claim 5 and wherein the steps of moving primary air to the air induction box and of continuously exhausting air from the air induction box comprise continuously exhausting air from the air induction box at a rate higher than the highest rate at which primary air is moved to the induction box.

7. An air induction box for use in a ceiling plenum with an air conditioning system that provides a flow of primary air, said induction box comprising a housing with a primary air inlet conduit for connection to the flow of primary air of the air conditioning system, a constantly open secondary air inlet for continuous constant pressure open communication with the ceiling plenum, an air outlet, an air outlet fan means arranged to move air from said housing through said air outlet, and valve means positioned in said primary air inlet conduit with an external sensor for regulating the flow of primary air from said primary air inlet conduit and into said induction box in response to changes in an external condition, said valve means being responsive to changes in air pressure upstream of said valve means to increase the opening through said primary air inlet conduit in response to a decrease in pressure in the primary air moving into the induction box and to reduce the opening through said primary air inlet conduit in response to an increase in pressure in the primary air moving into the induction box, whereby when the valve means reduces the flow of primary air into the housing 8 the fan means induces more air to flow from the ceiling plenum through the secondary air inlet and into the housing, and when the valve means increases the flow of primary air into the housing the fan means induces less air to flow from the ceiling plenum through the secondary air inlet and into the housing, and the valve means opens further in response to a decrease in pressure in the primary air moving into the induction box and closes further in response to an increase in pressure in the primary air moving into the induction box to maintain a substantially constant flow of primary air into the induction box in spite of rapid changes in pressure of the primary air moving into the induction box. 

1. An air induction box comprising a housing with side walls and opposed end walls, a primary air conduit entering said housing through a first end wall and extending into said housing with its end opening extending toward the second end wall, at least one unrestricted secondary air inlet opening in said housing adjacent the entrance of said primary air conduit into said housing, a substantially constant speed centrifugal blower in said housing including an exhaust conduit extending through the second end wall arranged to continuously exhaust mixed air from said housing at a substantially constant rate, a sound baffLe in said housing, valve means in the portion of said primary air conduit extending into said housing for selectively decreasing or increasing the flow of primary air through said primary air conduit, said valve means comprising a venturi in said primary air conduit, a valve support rod in said primary air conduit upstream from said venturi movable along its length toward and away from said venturi, a valve ball mounted on and movable with said valve support rod toward and away from said venturi and spring means connected between said valve ball and said valve support rod and arranged to permit relative movement between said valve ball and said valve support rod and to bias said valve ball away from said venturi, whereby the valve ball moves along the length of the valve support rod in response to differential air pressure across the valve ball and regulates the flow of primary air into the housing.
 2. Air air induction box comprising a housing, a primary air conduit entering said housing, at least one unrestricted secondary air inlet opening in said housing, a substantially constant speed blower arranged to continuously exhaust mixed air from said housing at a substantially constant rate, valve means in said primary air conduit for selectively decreasing or increasing the flow of primary air through said primary air conduit, said valve means comprising a venturi in said primary air conduit, a valve support rod in said primary air conduit upstream from said venturi movable along its length toward and away from said venturi, a valve ball mounted on and movable with said valve support rod toward and away from said venturi and spring means connected between said valve ball and said valve support rod and arranged to permit relative movement between said valve ball and said valve support rod and to bias said valve ball away from said venturi, whereby the valve ball moves along the length of the valve support rod in response to differential air pressure across the valve ball and regulates the flow of primary air into the housing.
 3. An air induction box for use in a ceiling plenum with an air conditioning system that provides a flow of primary air, said induction box comprising a housing with a primary air inlet conduit for connection to the flow of primary air of the air conditioning system, a constantly open secondary air inlet for continuous constant pressure open communication with the ceiling plenum, an air outlet, an air outlet fan means arranged to move air from said housing through said air outlet, and valve means positioned in said primary air inlet conduit for regulating the flow of primary air through said primary air inlet conduit, said valve means comprising a venturi, a valve member positioned upstream of said venturi and movable toward and away from said venturi to reduce and increase the flow of primary air through said primary air inlet conduit and into said induction box and spring means biasing said valve member away from said venturi to permit the valve member to move toward and away from said venturi in response to changes in pressure upstream of said venturi, whereby when the valve means reduces the flow of primary air into the housing the fan means induces more air to flow from the ceiling plenum through the secondary air inlet and into the housing, and when the valve means increases the flow of primary air into the housing the fan means induces less air to flow from the ceiling plenum through the secondary air inlet and into the housing, and the spring means moves the valve member away from the venturi in response to a decrease in pressure in the primary air moving into the induction box and allows the valve member to move toward the venturi in response to an increase in pressure in the primary air moving into the induction box to maintain a substantially constant flow of primary air into the induction box in spite of rapid changes in pressure of the primary air moving into the induction box.
 4. The air induction box of claim 3 and wherein said prImary air inlet conduit comprises a conduit extending through a first end of said housing with an outlet opening spaced away from said one end of said housing, and wherein said valve means is positioned in a portion of said primary air inlet conduit which is located within said housing.
 5. An air ventilating process for a room having a ceiling plenum and an air induction box located in the ceiling plenum with a constantly open secondary air opening defined in the induction box comprising the steps of moving primary air at a first temperature through a conduit into the air induction box to a position downstream of the secondary air opening, continuously exhausting air from the air induction box at a substantially constant rate from a position downstream from the position where the primary air is moved from its conduit into the induction box and directing the exhausted air to the room below the ceiling, reducing the flow of primary air to the air induction box in response to a change in an external condition while continuing to exhaust air from the air induction box at a substantially constant rate so as to induce more air to flow from the ceiling plenum through the secondary air opening and into the air induction box, and increasing the flow of primary air to the air induction box in response to a change in an external condition while continuing to exhaust air from the air induction box at a substantially constant rate so as to induce less air to flow from the ceiling plenum through the secondary air opening and into the air induction box, and maintaining a substantially constant flow of primary air to the air induction box in spite of rapid increases or decreases in pressure of the primary air moving toward the air induction box.
 6. The system of claim 5 and wherein the steps of moving primary air to the air induction box and of continuously exhausting air from the air induction box comprise continuously exhausting air from the air induction box at a rate higher than the highest rate at which primary air is moved to the induction box.
 7. An air induction box for use in a ceiling plenum with an air conditioning system that provides a flow of primary air, said induction box comprising a housing with a primary air inlet conduit for connection to the flow of primary air of the air conditioning system, a constantly open secondary air inlet for continuous constant pressure open communication with the ceiling plenum, an air outlet, an air outlet fan means arranged to move air from said housing through said air outlet, and valve means positioned in said primary air inlet conduit with an external sensor for regulating the flow of primary air from said primary air inlet conduit and into said induction box in response to changes in an external condition, said valve means being responsive to changes in air pressure upstream of said valve means to increase the opening through said primary air inlet conduit in response to a decrease in pressure in the primary air moving into the induction box and to reduce the opening through said primary air inlet conduit in response to an increase in pressure in the primary air moving into the induction box, whereby when the valve means reduces the flow of primary air into the housing the fan means induces more air to flow from the ceiling plenum through the secondary air inlet and into the housing, and when the valve means increases the flow of primary air into the housing the fan means induces less air to flow from the ceiling plenum through the secondary air inlet and into the housing, and the valve means opens further in response to a decrease in pressure in the primary air moving into the induction box and closes further in response to an increase in pressure in the primary air moving into the induction box to maintain a substantially constant flow of primary air into the induction box in spite of rapid changes in pressure of the primary air moving into the induction box. 